System and method for vaporizing a cryogenic liquid

ABSTRACT

A flameless thermal oxidizer including a matrix bed containing media and an inlet tube extending into the matrix bed and having an outlet positioned to deliver reacting gases into the matrix bed is disclosed. The matrix bed defines a void proximal the outlet of the inlet tube. Also disclosed is a method of reducing pressure losses in a flameless thermal oxidizer including the step of introducing reacting gases from an inlet tube into a void defined by a matrix bed.

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. application is a divisional patent application claimingpriority to U.S. patent application Ser. No. 11/037,034, filed on Jan.18, 2005, which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

This invention relates to a system and method for vaporizing a cryogenicliquid and, more particularly, a system for providing heat for cryogenicliquid vaporization.

BACKGROUND OF THE INVENTION

It is often necessary or desirable to vaporize a cryogenic liquid (i.e.,to bring about vaporization of a cryogenic liquid to a vaporized state).For example, and though a wide variety of applications exist for liquidvaporization, it is often necessary or desirable to vaporize liquidnatural gas (LNG) so that it can be handled and distributed as a fuelsource.

Many vaporization systems operate with burners in order to produce thenecessary vaporization heat. For example, evaporators of the submergedcombustion type comprise a water bath in which a flue gas tube of a gasburner is installed as well as an exchanger tube bundle for thevaporization of the liquefied gas. The gas burner discharges thecombustion flue gases into the water bath, which heat the water andprovide the heat for the vaporization of a liquefied gas that flowsthrough the tube bundle. Such vaporization systems are provided, forexample, by T-Thermal Company, a division of Selas Fluid ProcessingCorporation, under the registered trademark SUB-X.

Evaporators of this type are reliable and of compact size, but they maybecome expensive to operate. For example, in order to reduce emissionsof nitrogen oxide (NOx) from such systems, a current practice utilizes agaseous fuel burner in combination with water injection to reduce NOxemissions. In such systems, NOx emissions can be reduced toapproximately 30 ppmvd, corrected to 3 volume percent oxygen (drybasis).

Further reduction of NOx emissions may require post combustion catalytictreatment. For example, a catalytic treatment system may be located atthe outlet of a submerged liquid bath. Such treatment utilizes a portionof the burner exhaust to reheat the gases that are exiting the liquidbath, so as to reduce the moisture content of the gases before theyenter the post combustion catalytic system. The corresponding use ofthis portion of the burner exhaust can, however, reduce the energyefficiency of the system, since this portion of the burner gases are notused to heat the cryogenic fluid.

Accordingly, there remains a need for an improved method and system forcryogenic liquid vaporization.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a flameless thermal oxidizeris provided. The flameless thermal oxidizer includes a matrix bedcontaining media, an inlet tube extending into the matrix bed and havingan outlet positioned to deliver reacting gases into the matrix bed. Thematrix bed defines a void proximal the outlet of the inlet tube. In theoxidizer, a disc is optionally positioned adjacent the outlet of theinlet tube and configured to direct reacting gases away from the inlettube. The void defined in the matrix bed is optionally substantiallycylindrical.

According to another aspect, this invention provides a method ofreducing pressure losses in a flameless thermal oxidizer, the methodincluding introducing reacting gases from an inlet tube into a voiddefined by a matrix bed.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be described with referenceto several embodiments selected for illustration in the drawing, ofwhich:

FIG. 1 is a schematic, block diagram of a vaporization system accordingto one exemplary embodiment of this invention;

FIG. 2 is a schematic diagram of an embodiment of a flameless thermaloxidizer capable of use in the vaporization system illustrated in FIG.1;

FIG. 3 is a schematic diagram of another embodiment of a flamelessthermal oxidizer capable of use in the vaporization system illustratedin FIG. 1;

FIG. 4 is a perspective view of yet another embodiment of a flamelessthermal oxidizer capable of use in the vaporization system illustratedin FIG. 1;

FIG. 5 is a perspective view of still another embodiment of a flamelessthermal oxidizer capable of use in the vaporization system illustratedin FIG. 1;

FIG. 6A is an elevation view of another embodiment of a vaporizationsystem according to this invention;

FIG. 6B is a plan view of the vaporization system illustrated in FIG.6A;

FIG. 6C is an elevation view of the vaporization system shown in FIG.6A, with portions removed to reveal internal details;

FIG. 7A is an elevation view of an embodiment of a manifold anddistributor assembly capable of use in the vaporization systemillustrated in FIG. 6A;

FIG. 7B is an end view of the manifold and distributor assemblyillustrated in FIG. 7A;

FIG. 7C is a cross-sectional, end view of the manifold and distributorassembly illustrated in FIG. 7A;

FIG. 7D is a plan view of a portion of the manifold and distributorassembly illustrated in FIG. 7A;

FIG. 8A is an elevation view of an embodiment of a tube bundle assemblycapable of use in the vaporization system illustrated in FIG. 6A; and

FIG. 8B is a cross-sectional end view of the tube bundle assemblyillustrated in FIG. 8A.

DETAILED DESCRIPTION OF THE INVENTION

The invention will next be illustrated with reference to the Figures.Such Figures are intended to be illustrative rather than limiting andare included herewith to facilitate explanation of the presentinvention. The Figures are not to scale, and are not intended to serveas engineering drawings.

A flameless thermal oxidizer (FTO) has been coupled with a cryogenicheat exchanger according to one aspect of this invention to vaporize aliquid such as liquefied natural gas prior to injection into a utilitydistribution system. The resulting vaporization system minimizes oxidesof nitrogen (NOx) emissions to the environment normally associated withconventional combustion processes. The thermal reaction of commercialfuel gas with air in a matrix bed of porous inert media is accomplishedusing the flameless thermal oxidizer. The reaction is optionallyconducted in an apparatus that is capable of establishing andmaintaining a non-planar reaction wave within the matrix bed.

Generally, and according to one exemplary embodiment, the vaporizationsystem includes a vessel that contains a matrix bed; one or more feedtubes that extend into the matrix bed; a burner or other matrix bedpreheat system; connecting ductwork to a heat exchanger (such as theSub-X® heat exchanger provided by T-Thermal Company of Blue Bell, Pa.);process controls; and an exhaust outlet to the atmosphere. A non-planarreaction wave (such as the one formed by the oxidizer shown in FIG. 3,for example) is established by heating at least a portion of the matrixbed to the minimum reaction temperature of a commercial fuel gas/airmixture and feeding said mixture at controlled rates into the feedtube(s). Upon exiting the feed tube(s), the commercial fuel gas/airmixture is reacted in a non-planar reaction wave to produce heat andnon-toxic combustion products.

The heat generated in the non-planar reaction wave maintains theinterior surfaces of the vessel at a temperature of at least 1600 degreeF. but less than 2400 degree F. during the entire operation, whichminimizes the formation of NOx emissions. The hot exhaust gases aredirected from the vessel through ductwork to a specialized cryogenicheat exchanger submerged in a water bath. Cryogenic liquids are directedthrough tubes in the interior of the heat exchanger as the quenchedexhaust gases contact the exterior surfaces of the tubes via the waterbath. The cryogenic fluid inside the heat exchanger completes a phasechange to a gaseous product resulting from the flow of heated gaseswithin the water bath. Exhaust gases exit the water bath and arereleased to the atmosphere via a stack.

The natural gas vaporization capacity of the system ranges from about150 to 200 million cubic feet per day, dependent on operating pressureconditions. Heat release rate for the flameless thermal oxidizer is 120MMBtu/hr, and the emission rate of nitrogen oxides is reduced.

The emissions of nitrogen oxides from the flameless oxidation processare approximately 2 ppmvd (corrected to 3 volume percent oxygen (drybasis)), which is significantly lower than the nitrogen oxide emissionsfrom the burner exhaust of the current practice. The use of theflameless oxidation eliminates the need for water injection, as well asthe post combustion catalytic NOx reduction treatment system. Thiselimination of the catalytic treatment system in turn eliminates thereoccurring use of both the catalyst and associated reducing agent (suchas ammonia). Catalyst has a limited operating lifetime and is expensiveto replace. The elimination of the reducing agent may make the systemsafer to operate by eliminating the storage and handling of ammonia. Theelimination of the post catalytic treatment system along with thenecessary heat input required to reheat the exhaust gases will increasethe system energy efficiency by utilizing all of the flameless oxidationexhaust to heat the cryogenic fluid.

Referring to the Figures generally, and according to one aspect of thisinvention, a system 1, 100 is provided for vaporizing a cryogenicliquid. To heat or vaporize fluids such as cryogenic liquids, the system1, 100 utilizes flameless oxidation to provide the heat input into asubmerged heat exchanger coil.

The system 1, 100 includes means for producing an exhaust gas byflameless thermal oxidation of a fuel/air mixture. For example, themeans for producing an exhaust gas optionally includes an oxidizer 2,10, 40, 70, 108 having a matrix bed 29, 42, 72,112; a fuel/air mixtureinlet 4, 54 positioned to deliver the fuel/air mixture to the matrix bed29, 42, 72,112; and an exhaust outlet 5, 45, 78A, 78B, 114 positioned todeliver the exhaust gas from the oxidizer 2, 10, 40, 70, 108.

The system 1, 100 also includes means for transferring heat from theexhaust gas to the cryogenic liquid. For example, the means fortransferring heat optionally includes a vaporizer 3 having a receptacle122 configured to hold a heat transfer medium; a conduit 118, 144 forcryogenic liquid extending into the receptacle; and a sparger 138positioned to deliver exhaust gas from the exhaust gas producing meansto the receptacle 122.

The heat transferring means of the system 1, 100 is coupled to receivethe exhaust gas from the exhaust gas producing means. In this manner,the products of reaction or oxidation in the exhaust gas producing meansare delivered to the heat transferring means. Such heat transfer bringsabout vaporization of a cryogenic liquid.

In use of system 1, 100, a fuel/air mixture is oxidized in a flamelessthermal oxidizer 2, 10, 40, 70, 108 to produce an exhaust gas. Heat isthen transferred from the exhaust gas to the cryogenic liquid, therebyvaporizing the cryogenic liquid. The oxidizing step optionally includesdelivering fuel/air mixture into a matrix bed 29, 42, 72,112, and thetransferring step optionally includes introducing exhaust gas into aheat transfer medium such as water.

To modify or retrofit a vaporizer of cryogenic liquid according to oneaspect of this invention, a flameless thermal oxidizer 2, 10, 40, 70,108 is coupled to the vaporizer 3, and the flameless thermal oxidizer 2,10, 40, 70, 108 is configured to deliver exhaust gas to the vaporizer 3.The coupling step optionally includes coupling an exhaust outlet 5, 45,78A, 78B, 114 of the flameless oxidizer 2, 10, 40, 70, 108 to a sparger138 of the vaporizer 3.

To reduce NOx emissions according to another aspect of the invention, afuel/air mixture is oxidized using a flameless thermal oxidizer 2, 10,40, 70, 108, and heat from exhaust gases generated by the oxidizing stepis transferred to a cryogenic liquid. The NOx emissions can be reducedto less than about 5 ppmvd NOx, preferably about 4 ppmvd NOx or less, ormore preferably about 2 ppmvd NOx or less, corrected to 3 volume percentoxygen (dry basis). The reduction of NOx emissions is optionallyperformed without catalytic treatment.

According to another aspect of this invention, a flameless thermaloxidizer 70 has a matrix bed 72 containing media, an inlet tube 80extending into the matrix bed 72 and having an outlet positioned todeliver reacting gases into the matrix bed 72. The matrix bed 72 definesa void 73 proximal the outlet of the inlet tube 80. A disc 82 isoptionally positioned adjacent the outlet of the inlet tube 80 andconfigured to direct reacting gases away from the inlet tube 80. Thevoid 73 is optionally substantially cylindrical.

To reduce pressure losses in a flameless thermal oxidizer, reactinggases can therefore be introduced from an inlet tube 80 into a void 73defined by a matrix bed 72. Also, plural exhaust outlets 78A, 78B can beprovided to exhaust reacted gases from the oxidizer 70.

It has been discovered that this invention provides an efficientvaporization technology with very low oxides of nitrogen emissions (NOx)resulting from the combustion of natural gas fuel. For example, atypical burner system may operate with up to 40 percent excess air in aLNG vaporizer as compared to approximately 175 percent excess air with aflameless thermal oxidizer. Such excess air is beneficial in that itlimits the maximum adiabatic temperature achieved in the oxidizer toless than the Zeldovich reaction mechanism requirements for high levelsof NOx production. Fuel consumption is unchanged when the burner andflameless thermal oxidizer technologies are compared, but the volume ofgases handled by the equipment is significantly larger for a flamelessthermal oxidizer system according to this invention.

A LNG vaporizer burner system together with water injection can produceNOx emissions in the range from 35 to 50 ppmvd. A LNG vaporizer using aflameless thermal oxidizer as the heat source according to thisinvention can produce NOx emissions in the range from 2 to 4 ppmvd,though NOx emissions lower than 2 ppmvd and greater than 4 ppmvd arecontemplated as well (the foregoing NOx emissions values being correctedto 3 volume percent oxygen on a dry basis).

In order to reduce NOx emissions (e.g., to comply with NOx emissionregulations), burner systems typically use post-combustion treatmentprocesses involving a catalyst and injection of a reducing agentchemical. These post-combustion control systems tend to be expensive,difficult to maintain, and require periodic shutdowns for catalystcleaning and replacement.

Referring specifically to the embodiments selected for illustration inthe figures, FIG. 1 provides a schematic illustration of an embodimentof a vaporization system, generally indicated by the numeral 1,according to one aspect of this invention. Vaporization system 1includes a flameless thermal oxidizer 2 that is coupled to a vaporizer3. The flameless thermal oxidizer 2 is configured to receive a fuel/airmixture 4 for reaction within the flameless thermal oxidizer 2.Flameless thermal oxidizer 2 is also configured to deliver exhaust gases5 that are produced as a result of the oxidation or reaction of thefuel/air mixture 4.

The vaporizer 3 is configured to receive the exhaust gases 5 from theflameless thermal oxidizer 2. The vaporizer 3 is also configured toreceive a cryogenic liquid 6 and to deliver a vaporized gas 7. Vaporizer3 is also configured to deliver emissions 8.

The hot exhaust gases 5 delivered from the flameless thermal oxidizer 2to the vaporizer 3 causes vaporization of the cryogenic liquid 6 into avaporized gas 7. Accordingly, the heat from exhaust gases 5 provides aheat source for the vaporization of the cryogenic liquid 6, and theexhaust gases 5 received in the vaporizer 3 from the flameless thermaloxidizer 2 are discharged from the vaporizer 3 in the form of emissions8 either for further treatment or discharge to the atmosphere.

FIG. 2 illustrates an exemplary embodiment of a flameless matrix bedreactor, generally designated by the numeral 10, which can be used inthe vaporization system 1 illustrated in FIG. 1 as a component of theflameless thermal oxidizer 2.

Referring to FIG. 2, there is shown a schematic of the internaltemperature zones in a flameless matrix bed reactor 10 that contains aplanar reaction wave 22. Additional details of the flameless matrix bedreactor 10 can be found in U.S. Pat. No. 6,015,540, which isincorporated herein by reference in its entirety.

The flameless reactor 10 includes a vessel 25, having a matrix bed ofporous inert media 29. The vessel is lined with a refractory material.Prior to the planar reaction wave, there is typically a cool zone 27that has a temperature below the uniform reaction temperature. After theplanar reaction wave 22, there will be a hot region 26 that is typicallyat least above 1200 degree F. By using temperature sensors 20, theplanar reaction wave 22 may be located within the matrix and moved to adesired point by controlling the output end of a process controller 28.

While this planar reaction wave temperature profile is effective foroxidation, corrosive products or reactants (such as acid gases or theirpre-cursors) can tend to condense in the cool zone 27 on the interiorsurfaces 23 of the vessel 25. This condensation can occur when thecorrosive products or reactants migrate through the lining of refractorymaterial 24 adjacent to the interior surfaces 23 of the vessel 25.Additionally, if the vessel is constructed of heat resistant metalalloys, and there is no internal lining of refractory material,corrosive products or reactants can still condense on the interiorsurfaces of the vessel in the cool zone 27. This condensation in turncan lead to corrosion of the interior surfaces of the vessel.Consequently, the life of the vessel can be reduced and/or moreexpensive materials of construction may be needed to improve corrosionresistance

FIG. 3 shows another embodiment of a flameless matrix bed reactor 40,which can be used to oxidize one or more chemicals. Additional detailsof the flameless matrix bed reactor 40 can be found in U.S. Pat. No.6,015,540.

Referring to FIG. 3, a flameless matrix bed reactor, generallydesignated by the numeral 40, is capable of use in the vaporizationsystem 1 illustrated in FIG. 1 as a component of the flameless thermaloxidizer 2.

As shown in FIG. 3, the flameless matrix bed reactor includes a vessel41, containing a matrix bed 42 of porous inert media; a vesselrefractory lining 63, located adjacent to the vessel interior surfaces64; a feed tube 43 for receiving a reactable process stream 44, where aportion of the feed tube 43 that passes through the vessel is insulatedwith a refractory lining 62; an exhaust outlet 45 for removing reactedprocess stream 46; and a void space 47 located above the matrix bed 42.The matrix bed 42 is heated by introducing a heated medium (flue gasesgenerated by a conventional fuel gas burner) 48, such as air, through aheating inlet 49. The reactable process stream is formed by combining ina mixing device 50 a fume stream 51 containing an oxidizable material,an optional oxidizing agent stream 52 (such as air or oxygen), and anoptional supplementary fuel gas stream 53.

After the reactable process stream is formed, it is fed into a feedinlet 54 of the feed tube 43. The reactable process stream is thendirected to the exit 55 of the feed tube 43. A non-planar reaction wave56 is established in the matrix bed located in a region approximatelyaround the exit 55 of the feed tube 43 and the bottom 57 of the vessel.The reactable process stream 44 is reacted (in this embodiment oxidized)in the non-planar reaction wave 56 to produce the reacted process stream46. The reacted process stream 46 is directed through the matrix bed 42,through the void space 47, and out the exhaust outlet 45.

The exhaust outlet 45 is positioned so that the reacted process stream46 prior to exiting the vessel 41 flows countercurrent to the flowdirection in the feed tube 43. The exhaust outlet 45 may be connected toeither the void space 47 or matrix bed 42. However, it is preferred thatthe exhaust outlet be connected to the void space 47. Temperaturesensors 58 may be used for monitoring the temperature in the flamelessmatrix bed reactor 40. A process controller 59 may be used for acceptinginput from the temperature sensors 58 and, in response thereto,controlling the flow rate of the reactable process stream 44, the fumestream 51, the optional oxidizing agent stream 52, the optionalsupplementary fuel gas stream 53, and/or the heated medium 48 (e.g.,flue gases generated by a conventional fuel gas burner).

FIG. 4 shows a schematic, perspective view of a flameless thermaloxidizer, generally indicated by the numeral 70, that can be used as acomponent of the flameless thermal oxidizer 2 of the vaporization system1 illustrated in FIG. 1. Flameless thermal oxidizer 70 includes a matrixbed 72 that extends upwardly to a top surface 74. The top surface 74 ofthe matrix bed 72 at least partially defines an oxidizer head space 76.

Dual, opposed exhaust ducts 78A and 78B are positioned to exhaustreacted gases from the oxidizer head space 76. Specifically, reactedgases that enter the oxidizer head space 76 from the matrix bed 72 aredelivered from the flameless thermal oxidizer 70 via exhaust ducts 78Aand 78B. The provision of dual, opposed exhaust ducts such as ducts 78Aand 78B has been discovered to reduce the pressure losses encountered bythe flameless thermal oxidizer 70.

Flameless thermal oxidizer 70 also includes a premixed gas dip tube 80that extends downwardly into the matrix bed 72 in order to deliver apremix of gas into the matrix bed 72 at a location below the top surface74 of the matrix bed 72. The dip tube 80 has a dip tube outlet diverterdisc 82 positioned adjacent the outlet of the premixed gas dip tube 80.The disc 82 helps to divert reaction gases away from the wall of the diptube.

Referring now to FIG. 5, a modification to the flameless thermaloxidizer 70 illustrated in FIG. 4 is shown. Specifically, as illustratedin FIG. 5, the flameless thermal oxidizer 70 is provided with amodification to its matrix bed 72 in order to improve the performance ofthe flameless thermal oxidizer 70. A void is created in the ceramicmedia bed or matrix bed 72 just beneath the dip tube outlet SO thatgases can flow with less restriction into the matrix bed 72 to lowerpressure losses in the flameless thermal oxidizer 70. The void isprovided in the form of a cylindrical voidage 73. In one exemplaryembodiment, the voidage 73 has a diameter of about 8 feet (correspondingroughly to the diameter of the dip tube outlet diverter disc 82) and adepth of about 3 feet.

While the embodiment of the voidage 73 illustrated in FIG. 5 issubstantially cylindrical in shape, it is contemplated that the voidagemay have a wide variety of geometric shapes (e.g., spherical or semispherical, elliptical, rectangular, or other geometric configurations).

Referring now to FIGS. 6A and 6B, another embodiment of a vaporizationsystem, generally indicated by the numeral 100, is illustrated.Vaporization system 100 includes a blower 102 configured to urge airinto the vaporization system 100. Downstream from the blower 102 is astart-up burner 104 used during start-up of the vaporizer system 100 topreheat the matrix bed (described later). Also downstream from theblower 102 is a fuel-air mixer 106 configured to mix fuel with the airintroduced by the blower 102.

The vaporization system 100 also includes a flameless thermal oxidizervessel 108 configured to receive the fuel-air mix provided by thefuel-air mixer 106. The flameless thermal oxidizer vessel 108 generatesthe heat that is used to vaporize liquid in the vaporization system 100.Specifically, hot gas is delivered from the flameless thermal oxidizervessel 108 via a hot gas duct 114.

From hot gas duct 114, hot gas is introduced into an SCV tank 122. Gasesare then delivered from the SCV tank 122 by means of an exhaustseparator 124 and an exhaust stack 126.

FIG. 6C is another elevation view of the vaporization system 100, withwall portions removed to reveal internal details of the flamelessthermal oxidizer vessel 108 and the SCV tank 122. The illustration inFIG. 6C also indicates the flow pattern of flue gases, indicated byarrows, in the flameless thermal oxidation vessel 108.

The flameless thermal oxidation vessel 108 includes a dip tube 110 thatextends downwardly into a ceramic packing 112. A mix of fuel and air isdelivered through the dip tube 110 into the ceramic packing 112 foroxidation or reaction within the ceramic packing 112. The flue gasesresulting from the reaction oxidation of the mixture of fuel and airtravels upwardly through the ceramic packing 112 into a space above theceramic packing 112 within the flameless thermal oxidation vessel 108,as indicated by the arrows in FIG. 6C. The flue gases are then urgedoutwardly from the flameless thermal oxidation vessel 108 and into thehot gas duct 114 for delivery to the SCV tank 122. The hot gas duct 114is preferably insulated in order to reduce loss of heat from the fluegases.

The SCV tank 122 is at least partially filled with a heat transfermedium such as water or other suitable medium. In operation, hot fluegases from the flameless thermal oxidizer vessel 108 are introduced intothe heat transfer medium such that it bubbles through the heat transfermedium, heats the heat transfer medium, and brings about heat transferfrom the heat transfer medium to cryogenic liquid flowing through atubing bundle situated in the heat transfer medium.

More specifically, the SCV tank 122 includes a manifold and distributorsystem such as assembly 116 connected to receive hot flue gases from thehot gas duct 114. Details of the manifold and distributor assembly willbe described later with reference to FIGS. 7A-7D. The SCV tank 122 alsoincludes a tube bundle 118 through which cryogenic liquid is circulatedfor vaporization. Further details of the tube bundle 118 will bedescribed later with reference to FIGS. 8A and 8B. Liquid natural gasinlet and natural gas outlet manifolds are provided in the SCV tank 122as indicated by numeral 120. It is by means of the inlet and outletmanifolds 120 that liquid natural gas is introduced into the tube bundleand the resulting natural gas is discharged from the tube bundle.

Referring now to FIGS. 7A through 7D, details of an embodiment of amanifold and distributor assembly are illustrated. The manifold anddistributor assembly, such as assembly 116, is configured to receive hotgases from the hot gas duct 114 and to deliver those hot gases into theheat transfer medium (e.g., water) in the SCV tank 122. Morespecifically, the manifold and distributor assembly 116 receives astream of heated gas and divides that gas for substantially evendistribution into the SCV tank to encourage heat transfer between thehot gases, the heat transfer medium, and ultimately the cryogenic liquidsuch as liquid natural gas circulating within the tube bundle 118.

Referring specifically to FIG. 7A, the manifold and distributor assembly116 includes a shell 128 that is substantially cylindrical in shape,though other cross-sectional shapes are contemplated as well. Shell 128is coupled to the hot gas duct 114 by means of a flange 130. Theopposite end of the shell 128 is capped by a plate 132. Plural liftinglugs 134 are provided along a top surface of the shell 128 in order tofacilitate the handling of the shell 128 during assembly, disassembly,modification and/or maintenance. Plural supports 136 are provided tosupport the shell 128 against a foundation of the SCV tank 122 (notshown).

In order to facilitate the distribution of hot gases from within theshell 128 to the heat transfer medium, the manifold and distributorassembly 116 is provided with plural spargers 138. Each sparger 138extends outwardly from the shell 128 and is connected to the shell 128in order to receive hot gases from the shell 128 and to deliver the hotgases to the heat transfer medium within the SCV tank 122.

Referring to FIG. 7B, which provides an end view of the manifold anddistributor assembly 116, the relationship between the sparger 138 andthe shell 128 of the manifold and distributor assembly 116 can be seen.Specifically, each sparger 138 extends outwardly from a lower portion ofthe shell 128 at an angle substantially transverse to the axis of theshell 128.

Referring to FIG. 7C, which provides a cross-sectional end view of themanifold and distributor assembly 116, each sparger 138 is provided witha closed end 140 and a plurality of openings 142 (generally positionedalong its upper surface) to permit the flow of hot gases from within thesparger 138 to the heat transfer medium in the SCV tank 122.

FIG. 7D provides a plan view of a portion of a sparger 138. Each sparger138 includes plural rows of openings 142 (two such row shown in FIG.7D). By means of openings 142, hot gas flows from within each sparger138 and into the heat transfer medium in the SCV tank 122.

While a specific embodiment of a manifold and distributor assembly 116is shown in the Figures for purposes of illustration, a wide variety ofconfigurations can be used in order to deliver hot gases to a heattransfer medium. Depending on a particular application or sizeconstraints for a vaporization system, the manifold and distributorassembly can have a wide variety of shapes, sizes, and configurations.Preferably, however, the assembly will be configured to distribute hotgases substantially evenly into heat transfer medium so that heat can besubstantially evenly distributed for the vaporization of cryogenicliquid.

Referring now to FIGS. 8A and 8B, an exemplary embodiment of a tubebundle configured for use in the SCV tank 122 is illustrated. The tubebundle 144 illustrated in FIG. 8A includes four (4) tubes, eachextending from an inlet 146 for liquid natural gas (or other cryogenicliquid) to an outlet 148 for vaporized natural gas (or other gas). Theinlet 146 and outlet 148 of tube bundle 144 correspond to the inlet andoutlet manifolds 120 illustrated in FIG. 6C.

As illustrated in FIG. 8B, which provides a cross-sectional end view oftube bundle 144 (with the tubes removed for clarification), the inlet146 and outlet 148 are provided with a plurality of openings forconnection to tube bundles such as tube bundle 144. Accordingly, aplurality of tube bundles 144 are positioned next to each other and areconnected for fluid flow communication with the inlet 146 and outlet 148in order to provide a dense population of flow passages through which acryogenic fluid can be passed for vaporization. For example, inlet 146and outlet 148 can accommodate up to fifteen (15) or more tube bundles144, each tube bundle 144 including four (4) tubes. In such anembodiment, the tube bundle assembly will provide sixty (60) tubes forthe flow of cryogenic liquid such as liquid natural gas (LNG). Each tubebundle 144 can also have fewer or more than four tubes, and the tubebundle assembly can have fewer or more than fifteen (15) rows of tubebundles.

EXAMPLE

According to one aspect of this invention, a flameless thermal oxidizercan be modified to create a cylindrical void at the diptube outlet.Also, a flat disc can be added to the end of the diptube to directreacting gases away from the diptube walls. These modifications were runon a CFD model and resulted in a significant reduction in pressurelosses and also changed the shape of the reaction wave to force improvedcontainment of the reaction gases within the ceramic media bed.

The flameless thermal oxidizer was setup in the CFD model with a 60 inchID by 20 foot long diptube. The ceramic media was simulated as 1 inchsaddles, such as those used in commercial applications, packed to adepth of 16 feet. The diptube was simulated as being immersed 8 feetinto the ceramic media bed. Two rectangular exhaust ducts were simulatedto be used to convey flue gases from the surface of the ceramic mediabed. The ducts were simulated to be installed 180 degrees apart in theheadspace above the ceramic media bed. Dimensions for the ducts weresimulated to be 2.5 feet high by 15 feet wide by 10 feet in length. Theoutlet of the diptube was simulated to be fitted with an 8 foot diameterdisc to divert reaction gases away from the diptube wall. A void wassimulated to be created in the ceramic media bed directly beneath thediptube outlet so that gases could flow with less restriction in anattempt to lower pressure losses in the flameless thermal oxidizer. Thevoid was simulated to be a cylindrical volume 8 feet in diameter and 3feet in height.

The LNG vaporizer was simulated to exert a 60 inch water column backpressure on the heat source due to pressure losses in the heat exchangertube bundle and water bath. Addition of the disc to the diptube outletand the void constructed in the ceramic medial bed significantly reducedthe pressure losses in the flameless thermal oxidizer. The reduction inpressure losses was simulated to be approximately 45 inches WC, yieldinga total pressure loss across the flameless thermal oxidizer of only 17inches WC.

According to the simulation, the velocity of the premixed gasestraveling down the diptube is approximately 50 feet per second. Thetotal mass flow rate is approximately 4400 lbs/min yielding a heatrelease of 122 MMBtu/hr HHV. Combustion air is supplied at the rate of4311 lbs./min and fuel gas at the rate of 86.26 lbs/min and, accordingto the simulation, the composition of the flue gases in volume percentis as follows:

Component Volume Percent Oxygen 13.38 Nitrogen 76.54 Carbon Dioxide 3.32Water Vapor 6.77

The gas velocity profile has been discovered to be significantlydifferent in the ceramic bed with the optional cylindrical voidagebeneath the diptube outlet, which contributes to a significant reductionin static pressure losses. Specifically, the temperature profile withinthe flameless thermal oxidizer after having installed the diptube exitdisc and the voidage beneath the diptube differs from that of aflameless thermal oxidizer having ceramic media packing at the diptubedischarge point and no disc attached to the diptube outlet. Also, it hasbeen discovered that less carbon monoxide is present in the headspaceabove the ceramic media surface as compared to the unmodified oxidizermodel. Although carbon monoxide burnout is achieved prior to the exhaustducts in both designs, this feature is an improvement and lends moreoperational flexibility to the process.

The CFD modeling results for a flameless thermal oxidizer with adiverter disc mounted on the discharge of the diptube and a cylindricalvoidage located beneath the diptube discharge have indicated asignificant reduction in static pressure losses across the oxidizer.This improvement benefits the operating economics for the flamelessthermal oxidizer in the LNG vaporizer application. Pressure lossesacross the flameless oxidizer now amount to only 17 inches WC.

Assuming that the pressure loss across the LNG vaporizer heat exchangeris not impacted by the flameless thermal oxidizer flue gas flow rate,then the total system pressure loss has been reduced from 122 inches WCto 77 inches WC. This represents a 37 percent reduction in pressurelosses with the flameless thermal oxidizer modifications presented here.The pressure loss reduction across the flameless thermal oxidizer aloneis a significant 72.6 percent with the modified design.

The temperature profile indicates that the reaction wave is betterconfined to the ceramic media bed with the modified design. While it hasbeen generally considered acceptable for there to be some cold gasbreakout into the headspace without a loss in performance, the reactionwave should remain within the ceramic media bed in order to increase therobustness of the flameless thermal oxidizer and reduce any perceptionof loss in performance associated with cold gas breakout.

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

For example, the specific structures of the vaporizer and the flamelessthermal oxidizer are not critical to the invention and may be modifiedwithin the scope of this invention. A wide variety of heat sources andheat exchangers can be utilized according to aspects of this invention.Similarly, the orientation of a heat exchanger (such as a vaporizer)with respect to the heat source (such as a flameless thermal oxidizer)can be modified to meet specific operating parameters.

While preferred embodiments of the invention have been shown anddescribed herein, it will be understood that such embodiments areprovided by way of example only. Numerous variations, changes andsubstitutions will occur to those skilled in the art without departingfrom the spirit of the invention. Accordingly, it is intended that theappended claims cover all such variations as fall within the spirit andscope of the invention.

What is claimed:

1. A flameless thermal oxidizer comprising: a matrix bed containingmedia; and an inlet tube extending into said matrix bed and having anoutlet positioned to deliver reacting gases into said matrix bed; saidmatrix bed defining a void proximal said outlet of said inlet tube. 2.The flameless thermal oxidizer of claim 1, further comprising a discpositioned adjacent said outlet of said inlet tube and configured todirect reacting gases away from said inlet tube.
 3. The flamelessthermal oxidizer of claim 1, said void being substantially cylindrical.4. A method of reducing pressure losses in a flameless thermal oxidizercomprising introducing reacting gases from an inlet tube into a voiddefined by a matrix bed.
 5. The method of claim 4, wherein theintroducing step comprises introducing gases from an inlet tube into acylindrical void defined by the matrix bed.
 6. The method of claim 4further comprising the step of directing reacting gases away from saidinlet tube by a disc positioned adjacent the outlet of the inlet tube.7. A flameless thermal oxidizer that is configured for reducing pressureloss of reacting gases comprising: a matrix bed containing media; and aninlet tube extending into said matrix bed and having an outletpositioned to deliver reacting gases into said matrix bed; and a discpositioned adjacent said outlet of said inlet tube and configured todirect reacting gases away from said inlet tube; said matrix beddefining a void proximal said outlet of said inlet tube that issubstantially devoid of media, wherein said outlet of said inlet tube ispositioned to deliver reacting gases into said void defined in saidmatrix bed in order to lower pressure losses of the reacting gases inthe flameless thermal oxidizer.
 8. The flameless thermal oxidizer ofclaim 7 said void being substantially cylindrical.
 9. The flamelessthermal oxidizer of claim 8 wherein a ratio of a diameter dimension ofsaid substantially cylindrical void to a depth dimension of saidsubstantially cylindrical void is about 8:3.
 10. The flameless thermaloxidizer of claim 8 wherein a ratio of a diameter dimension of saidsubstantially cylindrical void to a depth dimension of saidsubstantially cylindrical void is at least about 8:3.
 11. The flamelessthermal oxidizer of claim 8 wherein a ratio of a depth dimension of saidsubstantially cylindrical void to a diameter dimension of saidsubstantially cylindrical void is at least about 3:8.
 12. The flamelessthermal oxidizer of claim 7 wherein said void is bounded by media andsaid outlet of said inlet tube.
 13. The flameless thermal oxidizer ofclaim 7, said inlet tube having an inlet for receiving a fuel and airmixture, wherein said inlet is disposed opposite said outlet of saidinlet tube and said inlet is positioned outside of said matrix bed.